Ball joints known from the prior art comprise a housing inside which a ball is arranged. The ball is part of a ball stud, which projects outward through an opening of the housing. Between the ball and the housing there is a ball shell, whose thickness is constant all the way round the circumference, around the common axis. When this ball shell is loaded radially, as the load on the stud or ball increases the ball is displaced radially relative to the housing. This displacement takes place parallel to the direction of the force and results in a compression of the ball shell, which is maximum in the direction of the force. In the direction transverse to the force the ball shell is not compressed and therefore not loaded, because in this case the ball is displaced parallel to the surface of the ball shell. Along the circumference or equator of the ball, the compression and hence the loading of the ball shell varies according to the vector component of the surface normals to the force direction. Thus, the ball shell is very non-homogeneously loaded, so that particularly under high loads the ball shell can be overloaded in the more highly loaded areas. This can cause permanent damage to the ball joint.
The maximum load-bearing capacity of ball joints can be increased if the loading is distributed more uniformly over all areas, in such manner that the load is spread homogeneously over as wide an angular area as possible between the radial force direction—and the two transverse directions perpendicular thereto (the transverse and vertical axes). In this case the vertical axis corresponds to the longitudinal axis of the joint housing. For the vertical axis directed parallel to the longitudinal axis, it is known that the thickness of the ball shell is not constant, but corresponding to the various inside contours of the housing (cylindrical or partially spherical contours, contours with a ramp or a double ramp), has wall thicknesses that increase or vary toward the pole of the ball. In other words, the thickness of the ball shell varies in the direction of the vertical axis.
For the transverse axis, which runs parallel to the equatorial plane, in the prior art the wall thickness is always constant because the openings of the housing are for example produced by boring and are radially symmetrical relative to the vertical axis.